Well I'm a regular MS and FOSS user and I must say that, while the MS Vista UAC prompt for limited users is important and valuable for security, from an administrator's POV the feature becomes at least an annoyance. MS says that UAC helps security, and that the internals of UAC are such that it protects the OS from malware. Indeed, if you are running a LU account, having the OS confirm that you have the rights to perform the task that you are doing can be a lifesaver, especially if you are a novice computer user. However, if you are running as an administrator you *should* be able to have unrestricted access to your system, just like running as root in Unix and Unix-like FOSS OSes (ah, the power of having the sharp sign...*sniff*). Honestly, having a dialog first telling me that I will need to supply credentials before, say, deleting a no-longer used folder under Program Files and then popping me another dialog to prompt me to confirm that I'm going to delete it is a, uh, sophomorical approach to security. Of Course I'm doing this, I'm the (expletive removed) administrator, the OS should not ask me this! *pause for breath*. Linux never asked me for permission to rm -rf /dev as root, not that it would be a good idea, of course...
Anyhow if you are running as LUA under vista I can see why you need UAC, but an administrator should not, must not have these annoyances, it's wasted time. There, those are my $0.02.

Paul Thurrott's scathing article Where Vista Fails highlights my biggest concern with Windows Vista: Modern operating systems like Linux and Mac OS X operate under a security model where even administrative users don't get full access to certain features unless they provide an in-place logon ...